How are Odds and Probabilities Calculated in Sports Betting

How are Odds and Probabilities Calculated in Sports Betting?

Sports betting, a popular activity, involves predicting sports results and placing a wager on the outcome. To be successful, bettors must understand the influence of odds and probabilities in sports betting. These two aspects play a crucial role in determining the potential payout of a bet and the chances of winning.


Odds are numerical values that show the potential return on a bet, relative to the amount staked. They are typically presented in three formats: decimal, fractional, and American odds.

Decimal odds are the easiest to understand. They indicate the total amount a bettor will receive for every dollar bet. For example, if a football team has odds of 1.5 and you place a $10 bet, your total return would be $15 ($10 x 1.5).

Fractional odds, commonly used in horse racing, show the potential winnings for every dollar staked. For instance, odds of 3/1 mean a successful $1 bet would lead to a $3 win, totaling $4.

American odds are a bit more complicated. A minus (-) figure, such as -150, shows how much money you need to stake to win $100. A positive (+) number like +200 indicates how much you’d win from a $100 bet.


Probability focuses on the chance of a certain outcome occurring and is presented as a value ranging from 0% to 100%. To calculate probability from fractional odds, use the formula denominator/(denominator+numerator) x 100. For example, odds of 3/1 would mean a 25% chance of winning.

For decimal odds, the formula is 1/decimal odds x 100. With odds of 1.5, the probability would be ~66.7%.

For American odds, the calculations differ for favorites and underdogs. For favorites, it's -odds/(-odds+100) x 100. For underdogs, it's 100/(odds+100) x 100. For example, if the odds are -200, the probability is ~66.7%. If the odds are +200, the probability is ~33.3%.

Sportsbooks use statistical data, current form, historical performance, injuries, and public sentiment to calculate and adjust odds and probabilities. Their goal is to establish a balanced book where the potential payout is roughly equal, regardless of the outcome. This means they are highly sensitive to fluctuations in betting activity and adjust odds accordingly.

The conversion between odds and probabilities is essential for bettors. A lower odd indicates a higher probability of winning, but also means lower potential winnings. This trade-off is why experienced bettors look for "value" in odds, where they believe the odds reflect a probability less than the actual likelihood of the event occurring.

In conclusion, understanding how odds and probabilities are calculated in sports betting is crucial for any bettor. These calculations not only provide insight into potential winnings but also inform how likely an event might occur. Armed with this knowledge, bettors can make informed decisions, mitigate risks, and maximize potential returns.